Authors:

Sandro Iannaccone

Wim J.G. Oyen

Abstract

Nuclear medicine, with its 80-year history, is a constantly evolving medical specialty. This article reviews its key milestones in Europe, focusing on diagnostic and therapeutic innovations, key figures, and prospects. It highlights European contributions to this field, which utilizes radioactive tracers for diagnosing and treating various pathologies, especially oncological ones. Nuclear medicine’s history is rooted in late 19th-century discoveries like X-rays (1895) and radioactivity (1896). The tracer principle, crucial to nuclear medicine, was developed by the Hungarian radiochemist and Noble Prize laureate George de Hevesy. Early clinical studies with radioisotopes focused on the thyroid, with the American physician Saul Hertz pioneering radioactive iodine therapy. In the 1950s-70s, isotopes expanded to other areas, with the development of gamma cameras. Imaging techniques like SPECT and PET revolutionized diagnostics, enabling the visualization of physiological and pathological processes at a molecular level. The introduction of ¹⁸F-fluorodeoxyglucose (FDG) significantly impacted PET in oncology. Computed tomography (CT) also played a vital role by integrating with nuclear medicine, improving diagnostic accuracy. The new millennium saw an exponential growth in the application of PET/CT and in the development of novel radiopharmaceuticals, resulting in the rise of radioligand therapy and the concept of theranostics, using the same molecular agent for diagnosis and therapy. Future frontiers include targeted radiopharmaceuticals, personalized dosimetry, and ever closer collaboration with other medical disciplines. Challenges involve new increased demands for radiopharmaceutical production and advanced imaging technologies, including radiomics. Nuclear medicine remains a fundamental discipline with a significant impact on clinical practice and biomedical research, and the European contributions to the field have been at the core of its development, offering as well great potential for the future of diagnosis and therapy in a wide variety of diseases.

Introduction

Nuclear medicine is a captivating and continuously evolving medical specialty, with roots in the scientific and technological discoveries of the late 19th century. The discovery of X-rays by the German physicist Wilhelm Conrad Röntgen in 1895 and of natural radioactivity by the French physicist Henri Becquerel in 1896 and the pioneering research of the Polish-French couple Marie and Pierre Curie, all Noble Prize laureates, marked the beginning of a new era in medical diagnostics and therapy. These events not only expanded our understanding of matter and energy but also laid the foundation for the development of innovative techniques capable of exploring the human body at the molecular level.

The key concept underlying nuclear medicine is the tracer principle, conceived by George de Hevesy, who is considered the “father” of this specialty ^[1]. This principle states that minute quantities of radioactive substances, called radiopharmaceuticals, can be introduced into the body to study biological processes without significantly altering or disrupting their functions ^[2]. De Hevesy used this principle to study the metabolism of various substances in the body, paving the way for a wide range of clinical applications. Notably, he demonstrated that bones are dynamic, constantly taking up and releasing phosphorus atoms ^[3]. De Hevesy’s work also included early metabolic studies that initiated the development of nuclear medicine.

The initial steps of nuclear medicine in clinical practice focused mainly on the study and treatment of thyroid gland. Saul Hertz pioneered the use of radioactive iodine (RAI) for the therapy of hyperthyroidism ^{[4] [5]} , demonstrating the potential of radioisotopes for targeted treatment of specific pathologies of the thyroid. His question, “Could iodine be made artificially radioactive?”, paved the way for radioiodine therapy. These early studies laid the groundwork for future therapeutic and diagnostic applications.

In the following years, nuclear medicine experienced rapid expansion, with the development of new imaging equipment such as the rectilinear scanner and the gamma camera. These instruments made it possible to visualize the distribution of radiopharmaceuticals within the body, offering valuable information on the functional status of different organs and tissues. The introduction of single-photon emission computed tomography (SPECT) and positron emission tomography (PET) represented a breakthrough in diagnostic imaging. PET, with the advent of ¹⁸F-fluorodeoxyglucose (FDG) ^[6], became an essential tool in oncology for the diagnosis, staging, and monitoring of response to therapy for various tumors. The radiopharmaceutical scientist Tatsuo Ido was one of the pioneers in the synthesis of FDG.

The collaboration of nuclear medicine with other medical specialties, such as radiology, oncology, and neurology, has led to the development of hybrid imaging techniques, such as PET/CT and SPECT/CT, which combine functional and anatomical information, improving diagnostic accuracy ^[7]. The introduction of PET/MRI is further expanding the clinical applications of hybrid imaging.

Today, nuclear medicine not only provides powerful diagnostic tools, but is also rapidly expanding its therapeutic indications. The use of therapeutic radionuclides, such as iodine-131 (131I) for thyroid cancer, and the development of the concept of theranostics, which allows the use of the same radiopharmaceutical for diagnosis and therapy, represent areas of great interest and rapid growth. For example, ²²³Ra-chloride is used to treat bone metastases, and ¹⁷⁷Lu-DOTATOC therapy for neuroendocrine tumors and ¹⁷⁷Lu-PSMA for treatment of prostate cancer demonstrate the importance of specific radiopharmaceuticals.

The prospects of nuclear medicine are promising, with the research of new radiopharmaceuticals targeted to specific cellular epitopes, the development of personalized dosimetry techniques, and the integration with new imaging technologies such as PET/MRI and new PET/CT techniques. Despite the progress made, nuclear medicine faces important challenges, such as the development of new methods to produce medical radioisotopes, the improvement of imaging technology, and the need for investments in research to overcome current limitations and fully exploit the potential of this discipline. The development of cyclotrons for radioisotope production has also been a key milestone. The use of accelerator-based neutron sources is also being explored for Boron Neutron Capture Therapy (BNCT).

The origins: the discovery of radiation and radioactivity (1895-1930s)

The story of nuclear medicine begins with the discovery of X-rays by German physicist Wilhelm Conrad Röntgen in 1895. While studying light emissions generated by electrical discharges in a Hittorf-Crookes tube, Röntgen noticed that a fluorescent screen nearby was emitting light. On November 8, 1895, Röntgen discovered that these rays penetrated matter and projected the image of the bones of his hand onto a screen. This observation, made while the tube was covered in black paper and the room was darkened, demonstrated the penetrating properties of these rays. Röntgen spent several weeks experimenting with these new rays, and on December 28, 1895, he presented a report entitled On the Use of the New Rays including an image of his wife’s hand obtained with a 30-minute exposure on a photographic plate. By 1896, X-rays had become an established tool in medicine, and in 1901 Röntgen was awarded the Nobel Prize in Physics for his discovery.

Another crucial event was the discovery of radioactivity by French physicist Henri Becquerel. In 1896, Becquerel, inspired by the discovery of X-rays and hypothesizing a connection with fluorescence, began to study uranium salts. Initially, Becquerel thought that exposure to sunlight was necessary for the emission of radiation, but he discovered that uranium salts emitted radiation capable of impressing photographic plates even in the dark. This led him to conclude that the emission of radiation was an intrinsic property of uranium and did not depend on external sources. An interesting episode is linked to this experiment: Becquerel left photographic plates wrapped in black paper and some uranium salts in a drawer. When he developed them, he noticed that the plates had been impressed, even though they had not been exposed to sunlight, and this led him to the conclusion that uranium emitted radiation spontaneously. Just two years after Röntgen, Becquerel was awarded the 1903 Nobel Prize in Physics for his discovery of radioactivity. There is a controversy surrounding Becquerel’s discovery, as French chemist Niepce de Saint Victor made similar observations about the effects of uranium on photographic plates about 40 years earlier, but did not get credit for it.

Early development of nuclear medicine: from the tracer principle to the first radiopharmaceuticals (1950s-1970s)

The period between 1950 and 1970 represents a crucial phase for the rapid evolution of nuclear medicine, marked by fundamental discoveries and the introduction of new technologies that transformed medical diagnostics and therapy. This era saw the formalization of the tracer principle, the development of specific radiopharmaceuticals, and the introduction of increasingly sophisticated instrumentation.

The fundamental concept underlying nuclear medicine is the tracer principle, first described by George de Hevesy, often regarded as the “father of nuclear medicine”. De Hevesy had the insight to use radioactive isotopes as indicators to study the behavior of stable atoms and molecules within biological systems. This principle is based on the idea that a minute amount of a radiopharmaceutical can participate in biological processes without altering or disturbing them.

De Hevesy applied this concept in various fields, from chemistry to biology. An interesting anecdote tells of how De Hevesy, while working in Ernest Rutherford’s laboratory in Manchester, used a radioactive isotope to reveal a habit of his landlady: suspecting that the meat served at lunch was recycled from dinner leftovers, he added a radioactive tracer to the leftover food and, a few days later, demonstrated with an electroscope that the lunch meat was radioactive. This episode, although unpublished, is a clear example of De Hevesy’s creativity and pioneering approach in the use of tracers. More seriously, De Hevesy used this method to study the solubility of lead salts, and he demonstrated that phosphorus is taken up and released by the skeleton. In 1943, De Hevesy was awarded the Nobel Prize in Chemistry for elucidating the tracer principle, solidifying his position as a pioneer in this discipline. His innovative vision paved the way for the use of radioactive isotopes to study metabolic and physiological processes in the human body.

The 1950s and 1960s saw the introduction of the first radioisotopes for medical use, with a focus on the study of the thyroid, brain, and bones. The interest in thyroid stemmed from the discovery that this organ absorbs iodine, an element that could easily be made radioactive. One of the first radioisotopes used was iodine-131 (¹³¹I), first produced in 1938. Initial studies with ¹³¹I focused on the treatment of hyperthyroidism, but its potential in the therapy of thyroid cancer was soon recognized. In particular, it was discovered that thyroid ablation was necessary for the treatment of metastases with radioactive iodine. In 1941, US physician Saul Hertz administered radioactive iodine to a patient, Elizabeth D., marking a crucial moment in the history of nuclear medicine. Subsequently, in 1946, Hertz published his study on the therapeutic use of radioactive iodine for hyperthyroidism. Other important radioisotopes used during this period were phosphorus-32 (³²P), mainly in the treatment of leukemia and polycythemia vera, and sodium-24 (²⁴Na), to trace the absorption of electrolytes. Also worth citing is technetium-99m (⁹⁹ᵐTc), introduced in the 1960s, that revolutionized diagnostic imaging, thanks to its short half-life (about 6 hours) and its ability to emit easily detectable gamma rays. The discovery of 99ᵐTc is attributed to P.V. Harper and collaborators, who proposed its use as a useful agent in 1962. 99ᵐTc rapidly became the most widely used radioisotope in diagnostic nuclear medicine.

Initially, the detection of radioactivity was carried out with Geiger-Müller counters, which were manually moved over the area of interest. This method was limited by its poor sensitivity, especially in the case of high gamma emissions, such as those of ¹³¹I. To overcome this problem, American biophysicist Benedict Cassen developed the first scintillators, replacing the detectors of GM counters with calcium tungstate crystals, improving the sensitivity in the detection of iodine. Subsequently, Cassen switched to thallium-doped sodium iodide crystals, added photomultiplier tubes to further increase sensitivity, and automated the system to scan the thyroid and produce an image. These developments led to the creation of the first rectilinear scanners, which allowed the measurement of the distribution of a radiopharmaceutical in an organ. Initially, rectilinear scanners were used to visualize iodine accumulation in the thyroid, to determine if a nodule was benign or malignant. These scanners, although rudimentary, represented an important step forward, paving the way for imaging other organs. One of the first brain scanners was nicknamed “hair dryer” or “head shrinker” because of its shape.

While the first rectilinear scanners provided valuable information, they were limited by their slow scanning speed and inability to image large areas of the body simultaneously. A significant advance in imaging technology was the development of the gamma camera, pioneered by American engineer Hal Anger in the late 1950s. Unlike rectilinear scanners, which used a single detector that moved across the body, Anger’s gamma camera used a large, stationary sodium iodide crystal that could detect gamma rays emitted from a wide area. The crystal was coupled to an array of photomultiplier tubes (PMTs) that converted the light emitted by the crystal into electrical signals, which were then processed to create an image. The first gamma camera used a film to record the image. Later, Anger replaced the film with an array of photomultiplier tubes, weighing together the signals from the tubes to localize the origin of the scintillation process and thus the origin of the registered gamma ray. The signals were then fed into the deflection plates of a cathode ray tube, and the single absorption events were registered on a photographic film until an image of the radionuclide distribution in the organ had been achieved.

This innovation dramatically increased the speed and sensitivity of nuclear medicine imaging, enabling the visualization of dynamic processes in organs, such as blood flow and perfusion. The Anger camera, as it became known, became the foundation for modern gamma cameras, revolutionizing the field of nuclear medicine. The design of the gamma camera has prevailed, although the performance has been greatly improved through the years, and digital technology has been introduced into its construction. The gamma camera is used to take 2-dimensional images and, when positioned on a rotating gantry, allows tomographic imaging (SPECT: single photon emission computed tomography). The camera employs collimators to achieve position resolution. Collimators are essential components of gamma cameras, designed to allow only gamma rays traveling in specific directions to reach the detector. This is achieved using lead septa that block photons not aligned with the detector and is critical for obtaining clear images. The introduction of the gamma camera represented a true breakthrough, enabling nuclear medicine to move from simple organ studies to dynamic imaging, which in turn led to the development of new diagnostic applications, particularly in the heart, lungs, and brain.

Parallel to the development of radioisotopes and instrumentation, there was intense research activity for the creation of radiopharmaceuticals, which are chemical compounds that contain a radioactive isotope and can be used to diagnose or treat various diseases. The first radiopharmaceuticals were relatively simple, often based on isotopes of elements naturally present in the body, such as iodine and phosphorus, but with the progress of research, more complex compounds were developed, with specific affinities for certain organs or tissues.

The introduction of macroaggregated human albumin labeled with iodine-131 in the early 1960s, for example, made it possible to study pulmonary perfusion, opening new perspectives in the diagnosis of pulmonary embolism. Understanding the mechanisms of radiopharmaceutical extraction by organs led to the development of techniques to measure blood flow in organs such as the liver and kidneys.

The rapid growth of nuclear medicine during this period led to the need to organize this new discipline in a structured way. However, the organizational approach varied considerably among different European countries. In some countries, such as the United States, nuclear medicine quickly became an independent medical specialty, with specific training programs and recognized certifications. In other countries, such as Sweden, nuclear medicine was integrated into other medical disciplines, such as radiology, clinical physiology, clinical chemistry, oncology, or hospital physics. This diversity of organizational approaches reflected the peculiarities of the health systems of the different countries and the different scientific traditions.

The Evolution of Diagnostics (1970s-2000s)

The period from 1970s to 2000s witnessed a significant transformation in nuclear medicine diagnostics, marked by the advent of new imaging technologies and the integration of contributions from physics, engineering, and computer science. This era saw the evolution of scintigraphy, the rise of computed tomography (CT), and the revolutionary impact of 18F-fluorodeoxyglucose (FDG) in positron emission tomography (PET).

Positron Emission Tomography (PET) emerged as a powerful imaging modality offering insights into metabolic processes. The first PET imaging instrument was developed in 1953, but it was not until the discovery of FDG that PET imaging achieved widespread clinical potential. PET utilizes radiotracers that emit positrons, which upon annihilation with an electron, produce two gamma rays that are detected by the scanner. The spatial correlation of these gamma rays allows for the reconstruction of images showing the distribution of the tracer.

The development of nuclear medicine during this period was heavily reliant on the contributions of physicists, chemists, engineers, and computer scientists. Physicists were instrumental in developing new detectors, such as the gamma camera and the PET scanner, as radiochemists were for the development of new radiotracers. Engineers also played a key role in designing and building the sophisticated equipment used in nuclear medicine. Computer scientists made crucial contributions to the field, developing algorithms for image reconstruction and processing, which are essential for both SPECT and PET. The evolution of computer technology allowed for the development of more sophisticated image reconstruction algorithms and more detailed and accurate simulations of tomographic systems. In Europe, research centers with accelerators and reactors played a key role in the education and training of scientific and technical personnel for nuclear medicine. These centers provided a stimulating environment for new ideas and innovative techniques, and they also served as a source of new radioactive isotopes.

The introduction of computed tomography (CT) marked a major advancement in diagnostic imaging, providing detailed anatomical information. The integration of CT with nuclear medicine techniques, initially through side-by-side or fused images, eventually led to the development of hybrid imaging systems, such as SPECT/CT and PET/CT. The combination of functional information from nuclear medicine scans with anatomical detail from CT greatly improved the accuracy of diagnosis and treatment planning.

As mentioned before, a pivotal development was the introduction of ¹⁸F-fluorodeoxyglucose (FDG), a radiolabeled glucose analog, which revolutionized PET imaging. Initially developed for brain imaging, FDG was found to be particularly useful for imaging myocardial metabolism and tumor metabolism, as tumor cells often have a high demand for glucose. The development of FDG opened the doors to the exploration of a wide range of diseases and conditions, including drug addiction, eating disorders, attention deficit hyperactivity disorder, Alzheimer’s disease, epilepsy, and coronary artery disease. The synthesis of FDG using 18F-fluoride, developed in 1986, was a major milestone. This synthesis gave a 50% yield in 50 minutes, required no added fluorine-19 and was amenable to automation, and its production time has since been reduced to under 30 minutes. FDG-PET scans can identify “hot spots” of tumor activity, even before anatomical changes are detected by other imaging techniques. This capability had a significant impact on cancer diagnosis, staging, and treatment monitoring, and has greatly expanded the clinical applications of PET imaging. The development of FDG represented a significant step towards the use of molecular imaging in clinical practice. While the initial work was done in the U.S. and Japan, in the 1990s, Europe led the way in generating evidence for the clinical value of PET. Key trials were conducted in the Netherlands and Switzerland, which played a pivotal role in expanding its use. At present, the introduction of radiomics and artificial intelligence may provide a further boost towards powerful applications of nuclear medicine technologies.

The Expansion of Therapy and the Concept of “Theranostics” (2000s-Present)

In the early 2000s, another major advancement took place: the introduction of hybrid machines. Initially, nuclear medicine imaging was conducted with standalone PET scanners, but these were soon combined with CT scanners, resulting in PET/CT hybrid machines. This revolutionized the field, combining the best of both imaging modalities and improving diagnostic accuracy. Following the success of FDG, several radiopharmaceuticals were developed for other indications. In oncology, we saw the introduction of tracers for neuroendocrine tumors and, notably, PSMA (prostate specific membrane antigen) imaging, which originated in Germany and significantly advanced prostate cancer diagnostics. Another key milestone was the development of PET/MRI hybrid machines. This innovation, introduced a few years after PET/CT, combined PET with MRI technology. However, PET/MRI remains more limited in use, mainly within research settings and university hospitals, compared to the widespread clinical application of PET/CT. Another significant step was the advent of larger imaging machines. Initially, cameras were relatively small, and patients had to be moved through them. More recently, whole-body PET scanners have been developed, allowing patients to fit inside the camera without movement, making scans incrementally faster and providing new opportunities for clinical and research applications.

The period from 2000 to the present has also seen a significant expansion in the therapeutic applications of nuclear medicine, along with the formalization of the concept of "theranostics." This era is characterized by the increased use of radioisotopes for targeted therapy, the development of new radiopharmaceuticals, and the growing importance of personalized dosimetry. Radionuclide therapy has become a crucial approach for treating various tumors and other pathologies, leveraging the targeted delivery of radiation to diseased tissues. A key application of this therapeutic modality remains the use of the abovementioned iodine-131 (¹³¹I) for the treatment of thyroid carcinoma: early work with radioisotopes in the 1940s demonstrated that the ablation of residual thyroid cells was necessary for the effective therapy of metastases. This groundbreaking finding transformed thyroid cancer from a terminal disease into a highly treatable condition, with overall survival rates reaching approximately 85%. ¹³¹I is also used to treat hyperthyroidism and goiter, with the aim of reducing or eliminating excess thyroid tissue. Other radioisotopes, such as strontium-89 (⁸⁹Sr), samarium-153 (¹⁵³Sm), lutetium-177 (¹⁷⁷Lu), and radium-223 (²²³Ra), are used for bone metastases, providing palliative relief and improving quality of life and in the case of 223Ra an increase of patient survival. Yttrium-90 (⁹⁰Y) is also used in targeted therapies such as peptide receptor radionuclide therapy (PRRT), radioimmunotherapy (RIT) and locoregional treatment of liver tumors and metastases with radiolabeled particles.

Europe played a leading role in developing somatostatin analogs for neuroendocrine tumor therapy. This research began in the 1980s in The Netherlands, led by Steven Lamberts and Eric Krenning and eventually led to an approved treatment, Lutetium-177 DOTATATE, which is now widely used in clinical practice. Similarly, research on prostate cancer imaging led to the development of Lutetium-177 PSMA, now an approved therapy which was initially developed by a German research group, led by the nuclear medicine physician Uwe Haberkorn. Today, it is increasingly used in treatment of metastatic prostate cancer. Currently, nuclear medicine plays a central role in treating patients with thyroid cancer, neuroendocrine tumors, and prostate cancer. However, research is ongoing, and new therapeutic agents are being developed for other malignancies. Over the next 10–15 years, radioligand therapy is expected to become an additional mainstream cancer treatment alongside chemotherapy, targeted therapies, and immunotherapy.

The concept of “theranostics” has emerged as a cornerstone of modern nuclear medicine, utilizing the same molecular agent for both diagnosis and therapy. This approach allows for precise targeting of diseased tissues, leading to improved therapeutic efficacy and reduced side effects. Again, iodine-131 is a prime example of this theranostic principle, where the same radioisotope is used for both imaging and therapy of thyroid diseases. The use of ¹²³I and ¹²⁴I for diagnostic purposes precedes the use of ¹³¹I for therapy. The ability to visualize the uptake of iodine in the thyroid and in metastatic sites enables a targeted and personalized approach to treatment. The theranostic approach allows clinicians to “see what you treat” and “treat what you see”, providing a more precise and personalized approach to patient care, and is expected to drive future advancements in oncology, as it allows clinicians to visualize precisely where a treatment is acting in the body and assess its effectiveness. It is like using the same tools for multiple purposes, from diagnosis to treatment monitoring, predictive testing, and prognostic testing: this makes nuclear medicine increasingly relevant in multidisciplinary oncology panels. Nuclear medicine specialists work closely with oncologists, hematologists, surgeons, urologists, and radiotherapists to determine the best ways to integrate nuclear medicine techniques into patient care.

Personalized dosimetry holds promise to fine-tune and optimize the therapeutic outcomes of radionuclide therapy. This involves using advanced mathematical and imaging techniques to estimate the dose delivered to tumors, as well as specific normal organs and tissues. Dosimetry may enable the customization of treatment plans to individual patients with the ultimate goal to effectively treat their disease while minimizing the risk of adverse radiation-related side effects. The use of dosimetry in radioiodine therapy was an early example of the importance of individualized treatment by adapting the administered dose to the specific characteristics of each patient’s disease. The more precise calculation of patient-specific dosimetry indicates a sophisticated understanding of the use of radionuclides.

Future prospect and conclusions

The field of nuclear medicine is continually evolving, with significant advancements expected in the coming years. Prospects include the emergence of new imaging techniques, innovative approaches to radioisotope production, and an increased emphasis on research and development. A key trend is the growing collaboration of nuclear medicine with other medical fields such as radiology, oncology, cardiology and neurology. This collaborative approach allows for a more comprehensive understanding of diseases and better-coordinated patient care. Technology has not reached its peak and there is still huge room for innovations that improve image quality, speed up scan or enhance diagnostic accuracy. For example, early PET scans took about one hour; now it is possible to complete them in under five minutes.

There is also an ongoing effort to develop new methods for the production of medical radioisotopes. This includes the use of particle accelerators and research reactors for creating isotopes that are not readily available from natural decay chains. Cyclotrons, in particular, have become a versatile tool for producing a wide range of radioisotopes used in nuclear medicine. New production facilities like MEDICIS, which uses proton beams from CERN, are being developed to improve the availability of high-quality isotopes. There is also a growing interest in alternative production methods for technetium-99m (⁹⁹ᵐTc), the most widely used radioisotope in nuclear medicine, including methods not fully relying on nuclear reactors. The development of new targetry methods and advancements in radiochemistry have also significantly impacted on the efficient production of medical radioisotopes.

Investment in research and development is crucial for the future of nuclear medicine. Research efforts are aimed at discovering new diagnostic and therapeutic techniques, optimizing existing ones, and improving patient outcomes. Emphasis is being placed on the development of new tracers for PET and SPECT that are very specific to certain diseases, particularly tumors. This includes the development of radiopharmaceuticals that target specific receptors on tumor cells. Large clinical trials are pivotal for validating the effectiveness of new treatments and imaging procedures. Research is also focused on improving image analysis and dosimetry methods for personalized treatment plans, so patients receive the optimal radiation dose to their cancers, while reducing side effects. Furthermore, research is needed for better understanding of radiobiology in the context of particle therapy.

One of the biggest challenges we face today is ensuring equitable access to these technologies across Europe. Nuclear medicine infrastructure is relatively expensive, and we need to make sure that all cancer patients, not just those in better resourced countries, can benefit from these advancements.